Method of making a balloon dilation catheter shaft having end transition

ABSTRACT

A catheter includes a balloon and a shaft having a coaxial portion including an outer tubular member having a bore, a transition neck, an access fitting adjacent the proximate end of the catheter shaft for directing a guidewire into the catheter shaft, an inflation port, a guidewire tubular member disposed coaxially in the outer tubular member, the outer tubular member and guidewire tubular member defining a first, annular inflation/deflation lumen fluid communication with the inflation port, at least one second inflation/deflation lumen separate from and non-coaxial with the guidewire tubular member and having a cross-sectional area less than the cross-sectional area of the first inflation/deflation lumen and opening at a proximate end into the first inflation/deflation lumen and at the distal end of the transition neck.

This application is a DIVISIONAL of U.S. patent application Ser. No.13/939,478, filed Jul. 11, 2013, and titled “Method Of Making A BalloonDilation Catheter Shaft Having End Transition”, now issued U.S. Pat. No.9,446,223, which is a DIVISIONAL of U.S. patent application Ser. No.12/355,659, filed Jan. 16, 2009, and titled “Balloon Dilation CatheterShaft Having End Transition,” now issued U.S. Pat. No. 8,728,110, issuedMay 20, 2014, the disclosures of which is incorporated by reference.

TECHNICAL FIELD

The disclosure relates to inflatable catheters and, specifically, toballoon dilation catheters. In particular, it relates to a balloondilation catheter having a catheter shaft including a coaxial portionand a transition neck with one or more lumens formed through thetransition neck.

BACKGROUND

Medical treatments using balloon dilation catheters, for example,Percutaneous Transluminal Angioplasty, have evolved to the point wheresuch treatments require the insertion of catheters into narrower andmore remote blood vessels within the body. This evolution has requiredthe use of catheters having correspondingly smaller shaft diameters andlonger shaft lengths. The migration toward catheters with smallerdiameter longer shafts presents several challenges, not the least ofwhich is catheter balloon inflation/deflation rates. As will beappreciated, as the diameter of catheter shafts has decreased thecross-sectional area available for inflation/deflation lumens hasdecreased. As the length of catheter shafts has increased, the pressuredrop along the length of the inflation/deflation lumen or lumens hasalso increased. Hence, the amount of time required to inflate or deflatecatheter balloons has increased as the diameter of catheter shafts hasdecreased and the lengths of such shafts has increased.

One conventional design for balloon dilation catheters is a coaxialdesign wherein two concentrically disposed tubular members form thecatheter shaft. The bore of the inner tubular member forms the guidewirelumen with the outer tubular member forming the catheter shaft body. Theannular space between the outer surface of the inner tubular member andthe inner surface of the outer tubular member forms aninflation/deflation lumen for transporting an inflation medium such as anoncompressible fluid to inflate and deflate the dilation balloon. Theinflation/deflation performance of a coaxial catheter is determined bythe difference in cross-sectional area between the inside diameter ofthe outer tubular member and the outside diameter of the inner tubularmember along with the length of the catheter shaft. For a givencombination of catheter diameter and guidewire lumen diameter, thecoaxial design is considered to maximize the cross-sectional areaavailable for the inflation/deflation lumen thereby providing the bestinflation/deflation performance for a given catheter length.

The balloon of a catheter utilizing the coaxial design is fastened atits proximal end to the distal end of the outer tubular member. Thedistal end of the balloon is fastened to the inner tubular member.However, the outer tubular member is not mechanically attached to theinner guidewire tubular member, rather the inner tubular member floatsfree within the outer tubular member. When inflated, the balloon maytend to elongate rather than expand in a radial direction since thedistal end of the balloon is attached to the inner tubular member whichmay move longitudinally relative to the outer tubular member. Thetendency to elongate detracts from the inflation performance of theballoon and additionally, places additional stresses on the joints wherethe proximal end of the balloon is attached to the outer tubular memberand where the distal end of the balloon is attached to the guidewiretubular member.

Other conventional catheter designs utilize non-coaxial and separateguidewire and inflation lumens. These non-coaxial designs are referredto as “multi-lumen” catheters even though it is appreciated that coaxialdesigns have multiple lumens as well. In keeping with industrypractices, for the purpose of this application, the term “multi-lumen”refers to designs wherein the guidewire lumen and inflation/deflationlumens are not coaxial. There are at least two types of multi-lumencatheter shafts: dual lumen shafts and extruded dual port shafts. Indual lumen shafts, a first tubular member forming the guidewire lumentherewithin and a second tubular member forming the inflation/deflationlumen therewithin run parallel to one another within a full diameterouter jacket surrounding both lumens. Since only the guidewire lumenmember and the inflation/deflation lumen member (i.e., not the outerjacket) are exposed to the balloon inflation pressure, only theserelatively small diameter tubular members need to be strong enough towithstand such pressures, and the full-diameter outer jacket of thecatheter can be made of a softer and/or thinner material.

The other type of multi-lumen catheter, i.e., the extruded dual portshaft has guidewire and inflation/deflation lumens that are integrallyformed longitudinal voids created during extrusion of the plastic orresin catheter shaft. The extrusion process enables construction of thecatheter shaft and the lumens in non-circular geometries such assemi-circular or crescent. However, for the same diameter, or crosssectional area, the geometry of extruded dual port shafts and dual lumenshafts is inferior to the coaxial design in terms of inflation/deflationperformance.

Hence, while multi-lumen shaft designs may present several advantagessuch as improved trackability, the cross-sectional configuration of suchcatheter shafts result in inflation/deflation performance that isinferior to that of coaxial shafts.

Thus, there exists a need for a balloon catheter having a shaft withinflation/deflation performance similar to that of a conventionalcoaxial design without the disadvantages thereof.

SUMMARY

In one aspect thereof, a shaft for a balloon dilation catheter to beutilized with a guidewire includes a catheter shaft having a coaxialportion including an outer tubular member having a bore, a proximateend, a distal end and a transition neck formed at the distal end of thecoaxial portion. The transition neck has a proximate end at the distalend of the outer tubular member and a distal end remote from the distalend of the outer tubular member. The shaft further includes an accessfitting adjacent the proximate end of the catheter shaft with an accessport for directing a guidewire into the catheter shaft and an inflationport for directing an incompressible inflation medium into the cathetershaft.

The catheter shaft includes a guidewire tubular member having a boredefining a guidewire lumen, a proximate end and a distal end. Theguidewire tubular member is disposed coaxially in the outer tubularmember between the access port of the catheter shaft and extendscontinuously through the outer tubular member to the distal end of theouter tubular member and through the transition neck. The outer tubularmember and guidewire tubular member define a first, annularinflation/deflation lumen therebetween in fluid communication with theinflation port, the first inflation/deflation lumen having a first crosssection and terminating at the transition neck.

At least one second inflation/deflation lumen is formed through thetransition neck. The second inflation/deflation lumen is separate fromand non-coaxial with the guidewire tubular member and has across-sectional area less than the cross-sectional area of the firstinflation/deflation lumen. The second inflation/deflation lumen opens ata proximate end thereof into the first inflation/deflation lumen and atthe distal end of the transition neck, providing fluid communicationfrom the first inflation/deflation lumen through the transition necksuch that inflation fluid passing through the first inflation lumen mayflow though the second inflation/deflation lumen and directly into adilation balloon attached to the transition neck to inflate or deflatethe dilation balloon.

In another aspect, the outer tubular member and the guidewire tubularmember are formed from thermoplastic weldable materials such as nylonand polyether block amide and the neck transition is formed by weldingthe outer tubular member to the guidewire tubular member. One or both ofthe guidewire tubular member and outer tubular member may be loaded withsufficient bismuth to make the catheter shaft at least partiallyradiopaque.

In one variation, the distal end of the transition neck is adapted forconnection to a proximal end of a dilation balloon, and the portion ofthe guidewire tubular member extending beyond the transition neck isadapted to pass through the interior of the dilation balloon and to beconnected to a distal end of the balloon.

In another aspect, a method of making a balloon catheter includespositioning a guidewire tubular member in the bore of an outer tubularmember such that the guidewire tubular member extends beyond the distalend of the outer tubular member. In one variation, the outer tubularmember and inner tubular member are formed from weldable thermoplasticmaterials and the inner tubular member has a bore defining a guidewirelumen. An annular space between the outside surface of the guidewiretubular member and the inside surface of the outer tubular memberdefines a first inflation/deflation lumen.

A first mandrel is placed into the bore of the guidewire tubular memberadjacent the distal end of the outer tubular member. At least one secondmandrel is placed into the annular space between the guidewire tubularmember and the outer tubular member adjacent the distal end of the outertubular member. The outer tubular member and inner tubular member areheated to weld the outer tubular member to the guidewire tubular memberat the distal end of the outer tubular member to form a transition neckwhereby the thermoplastic materials of the outer tubular member andinner tubular member are bonded around the second mandrel. In onevariation, the outer tubular member is welded to the guidewire tubularmember by compression thermal molding. A heat shrink material such as aPTFE tube may be placed around the distal end of outer tubular memberand the guidewire tubular member prior to heating the outer tubularmember and guidewire tubular member.

The second mandrel is removed from the transition neck to form a secondinflation/deflation lumen that extends from the firstinflation/deflation lumen and opens at the distal end of the transitionneck. A proximate end of a dilation balloon is attached to thetransition neck and the distal end of the dilation balloon is likewiseattached to the guidewire tubular member. The balloon may be attached tothe outer tubular member and guidewire tubular member by welding orgluing.

In one variation, the balloon is placed over the guidewire tubularmember with a proximate end of the balloon adjacent the distal end ofthe outer tubular member prior to welding the outer tubular to theguidewire tubular member. The proximate end of the balloon, the outertubular member and guidewire tubular member are heated to weld theproximate end of the balloon, the outer tubular member and guidewiretubular member together to form the transition neck. The proximate endof the balloon, the outer tubular member and guidewire tubular membermay be welded together using compression thermal molding.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings in which:

FIG. 1 is a side view of a balloon dilation catheter according to thedisclosure;

FIG. 2 is a first cross-section of the balloon dilation catheter shaftof FIG. 1 taken through a coaxial portion thereof;

FIG. 3 is a second cross-sectional view of the balloon catheter shaft ofFIG. 1 taken through the neck transition of the catheter;

FIG. 4 is a cross-section through the neck transition of the catheterillustrating an alternative lumen configuration;

FIG. 5 is a cross-section of the catheter of FIG. 1 taken through theballoon of the catheter;

FIG. 6 is a longitudinal section of the balloon and transition neck ofthe catheter of FIG. 1; and

FIG. 7 is a flow chart of a method for constructing one embodiment of acatheter of the disclosure.

DETAILED DESCRIPTION

This application incorporates by reference the disclosures of pendingU.S. patent application Ser. No. 11/158,855, published asUS2007-0010847A1, and pending U.S. patent application Ser. No.11/174,676, published as US2007-0016133A1.

Referring now to the drawings, wherein like reference numbers are usedherein to designate like elements throughout, the various views andembodiments of a balloon dilation catheter shaft having an endtransition are illustrated and described, and other possible embodimentsare described. The figures are not necessarily drawn to scale, and insome instances the drawings have been exaggerated and/or simplified inplaces for illustrative purposes only. One of ordinary skill in the artwill appreciate the many possible applications and variations based onthe following examples of possible embodiments.

Turning now to FIG. 1, in one embodiment a balloon dilation catheter 10includes a shaft 12 having a proximate end 14 and a distal end 18. Asset forth in detail below, a plurality of tubular members disposed incatheter 10 define internal, longitudinally extending passages known aslumens. In one variation, the tubular members are formed from weldablethermoplastic materials and one or more of the tubular members mayinclude a material, such as bismuth, for radiopacity.

Referring still to FIG. 1, one tubular member, the guidewire tubularmember, extends longitudinally through the catheter from access fitting16 to the distal end 32 of dilation balloon 20. The guidewire tubularmember 34 has a bore defining a guidewire lumen through which aconventional guidewire 22 may be directed through the interior ofcatheter 10. Access fitting 16 is attached to proximate end 14 of shaft12. As illustrated, access fitting 16 includes a first port 26 forreceiving a guidewire 22 therethrough and directing guidewire 22 intothe guidewire lumen in shaft 12. Access fitting 16 includes a secondport 28 adapted to receive an incompressible inflation medium and directthe medium into an inflation/deflation lumen in shaft 12. Guidewire 22may be provided with a manipulator 24 for rotating and positioning theguidewire from the proximal end of catheter 10.

Referring still to FIG. 1, a dilation balloon 20 is affixed to thedistal end 18 of shaft 12. Balloon 20 may be of conventionalconstruction and is typically formed of relatively non-distensibleplastic or polymer material such as nylon. The envelope of the balloonmay be plain or reinforced with filaments or fibers. For the purpose ofillustration, balloon 20 is shown in an inflated configuration in FIG. 1with portions of the envelope broken away to better to illustrate theinterior structure of the balloon. While balloon 20 is illustrated in aninflated configuration, it will be appreciated that when deflated theballoon can typically be folded in such a manner as to have an outsidediameter or cross section approximately equal to that of catheter shaft12. The dimensions of balloon 20 may also vary significantly from thatillustrated in FIG. 1 both radially and longitudinally.

Balloon 20 may be attached to distal end 18 of shaft 12 using varioustechniques known in the art. In the embodiment illustrated in FIG. 1,the proximate end 30 of balloon 20 is welded to shaft 12 as will bedescribed in detail below. In other embodiments, the proximal end 30 ofballoon 20 may be connected to shaft 12 of catheter 10 by means of amedical grade epoxy adhesive. The distal end 32 of balloon 20 isconnected with a fluid-tight seal to the outside (i.e. radial) surfaceof guidewire tubular member 34, which, as illustrated, extends beyondthe distal end of the catheter shaft, passing through the interior ofballoon 20. In one variation, the distal end 32 of balloon 20 is weldedto guidewire tubular member 34 in order to form a fluid-tight seal. Inother variations, the distal end 32 of balloon 20 may be adhered toguidewire tubular member 34 by means of a medical grade epoxy. In stillother variations, a thermoplastic shim (not shown) may be placed betweenthe distal end of tubular guidewire member 34 and the distal end ofballoon 32 in order to provide material from which the distal end ofcatheter 10 may be molded to provide a desired configuration or profile.

In order to obtain relatively high inflation/deflation rates, cathetershaft 12 is formed with a coaxial portion 15 and a transition neck 40.Coaxial portion 15 extends between access fitting 16 and transition neck40. Within coaxial portion 15, guidewire tubular member 34 defines aguidewire lumen while outer tubular member 44 defines aninflation/deflation lumen between the inside surface of the outertubular member and the outside surface of the guidewire tubular member.Outer tubular member 44 and guidewire tubular member 34 may be formedfrom a variety of suitable plastic materials. In the embodimentillustrated in FIG. 1, guidewire tubular member 34 and outer tubularmember 44 are formed from weldable thermoplastic materials such asnylon-11, nylon-12 and/or a polyether block amide (PEBA). In oneembodiment, guidewire tubular member 34 and/or outer tubular member 44may be formed from PEBA elastomers sold under the trademark Pebax(R).PEBA elastomers are available in plastizer and additive-free medicalgrades having a nominal hardness (Shore D) from about Shore D 30 toabout Shore D 72. The thermoplastic materials used to make tubularguidewire member 34 and outer tubular member 44 may be loaded withmaterials such as carbon nanotubes or similar materials in order toenhance the strength of the tubular members. In other variations,tubular guidewire member 34 and/or outer tubular member 44 may be loadedwith a radialopaque material such as bismuth. In one variation, tubularguidewire member 34 and/or tubular outer member 44 may be loaded with upto approximately twenty percent by weight bismuth.

FIG. 2 is a cross-section of catheter shaft 12 taken through coaxialportion of the shaft. As illustrated, tubular guidewire member 34defines a guidewire lumen 42 through which guidewire 22 passes. Outertubular member 44 defines an inflation/deflation lumen 46 between theinside surface of the outer tubular member and the outside surface ofthe guidewire tubular member through which an incompressible fluid maybe directed to inflate or deflate balloon 20. In one variation, an outercoating 48 may be applied to outer tubular member 44 to enhance theproperties of catheter 10. For example, coating 48 may be a radiopaquematerial to enhance the visibility of catheter shaft 12 by means ofradiography. Alternatively, coating 48 may be made of a material thatprovides a smooth exterior surface to minimize the tendency of bloodcells to accumulate and/or of a hydrophilic material that exhibitslubricity in contact with blood. As will be appreciated, the flexibilityof catheter shaft 12 may be varied along the length of the shaft byvarying the wall thicknesses of tubular guidewire member 34 and/or outertubular member 44 or by varying the composition of the materials fromwhich the tubular guidewire member and outer tubular member are formed.

FIG. 3 is a cross-section of catheter shaft 12 taken through transitionneck 40. As illustrated, transition neck 40 includes one or moresecondary inflation/deflation lumens 50. Secondary lumens 50 extend frominflation/deflation lumen 46 of coaxial portion 15 of catheter shaft 12through transition neck 40, opening into balloon 20. Secondary lumens 50are formed by inserting a mandrel or mandrels between outer tubularmember 44 and guidewire tubular member 34 prior to forming transitionneck 40. A mandrel is also positioned within guidewire tubular member 34in the region of neck 40 prior to forming the neck to preventobstruction of guidewire lumen 42. In one variation, transition neck 40may be formed by means of thermal compression molding as describedbelow.

Referring still to FIG. 3, in one variation, tubular guidewire member 34is positioned in outer tubular member 44 and mandrels are insertedbetween the guidewire tubular member and outer tubular member to formsecondary inflation/deflation lumens 50. A mandrel is also inserted intoguidewire tubular member 34 to prevent the guidewire tubular member fromcollapsing during the molding process. The mandrels may be formed from avariety of materials for example, stainless steel or PTFE so long as themandrels have sufficient mechanical strength and thermal resistance towithstand the heat and pressure of the molding process. In onevariation, a heat shrink material such as a Teflon (PTFE) film or tubeis placed around catheter shaft 12 in the region where transition neck40 is to be formed.

To form the transition neck, the region of transition neck 40 ofcatheter shaft 12 is heated to a temperature above the softening pointof the thermoplastics from which outer tubular member 44 and guidewiretubular member 34 are formed, typically between 300 degrees Fahrenheitand 400 degrees Fahrenheit. Heating the transition neck region 40 may beaccomplished in a number of different ways. For example, the transitionneck region 40 may be placed in a heated die. Alternatively, thetransition neck region 40 may enclosed in a heat shrink material andheated in a small oven. Alternatively, the transition neck region may beheated ultrasonically or with a laser. If a heated die is used, it maynot be necessary to use a heat shrink material since the die may beconfigured to compress the transition neck region during the heatingprocess.

Upon heating, the softened thermoplastic materials tend to flow togetheraround the mandrels to form secondary inflation/deflation lumens 50. Ina variation wherein a heat shrink material is used, the heating processcauses the heat shrink material to shrink, compressing the softenedthermoplastic materials together. Compression molding using a heatshrink material tends to eliminate irregularities or discontinuities inthe surface of transition neck 40. During the thermal compressionmolding process, the thermoplastic materials from which the innertubular member 34 and outer tubular member 44 are formed flow or bondtogether to form a continuous mass 52 that surrounds secondaryinflation/deflation lumens 50 and guidewire lumen 42 when the mandrelsare removed. In one variation mass 52 forms a fluid tight bond withguidewire tubular member 34 that mechanically attaches the guidewiretubular member to the outer tubular member. Notably, secondaryinflation/deflation lumens 50 are formed without the use of additionaltubes or hollow members.

Multiple secondary inflation/deflation lumens 50 may be formed duringthe thermal compression molding process. In the variation illustrated inFIG. 3, two secondary inflation/deflation lumens having a circularcross-section are formed. In other variations, different numbers ofsecondary lumens and/or different geometries may be used. For example,the cross-section of secondary inflation/deflation lumens 50 could besquare, triangular or polygonal. In the variation illustrated in FIG. 4,the cross-section of secondary inflation/deflation lumen 50 is crescentshaped. As will be appreciated, the geometry of inflation/deflationlumens will tend to match the outside profile of the mandrel or mandrelsplaced in the annular space between the guidewire tubular member andouter tubular member prior to heating.

Regardless of the particular geometry selected for secondaryinflation/deflation lumen or lumens 50, the cross-sectional area of thesecondary lumen or lumens will be less than the cross-sectional ofinflation/deflation lumen 46 of the coaxial portion 15 of catheter shaft12. Therefore, in order to minimize the pressure drop across transitionneck 40, it is preferred to make the neck as short as possible.Generally, the length of transition neck 40 must be sufficient toprovide a bond between outer tubular member 44 and guidewire member 34having sufficient mechanical strength to resist delamination underpressure. Further, the length of transition neck 40 should be sufficientto compensate for any material defects. Typically, the length oftransition neck 40 will be less than 10 mm. In some variations, thelength of transition neck 40 may be in the range of 2-4 mm.

FIG. 5 is a cross-section of dilation catheter 10 taken through balloon20 in a direction toward the proximal end of the catheter. In onevariation, balloon 20 is also formed from a thermoplastic material suchas PEBA, nylon-11 or nylon-12. In this variation, balloon 20 may bewelded onto catheter shaft 12 during the compression molding processwherein transition neck 40 is formed. Balloon 20 is positioned overguidewire tubular member 34 prior to the thermal compression moldingprocess with proximal end 30 in abutting relationship with the distalend of outer tubular member 44. The region of transition neck 40 is thenwelded by means of thermal compression molding as previously described.The use of a heat shrink material in this process causes thethermoplastic material of balloon 20 to soften and flow together withthe thermoplastic guidewire tubular member 34 and outer tubular member44. Line 54 in FIG. 5 represents the proximal end 30 of balloon 20 inabutting relationship with the distal end of outer tubular member 44.

As will be appreciated, transition neck 40 could also be formed by agluing process using, for example, a medical grade epoxy. In this case,mandrels would be inserted between outer tubular member 44 and innertubular member 34 as previously described to form secondaryinflation/deflation lumens 50. An adhesive such as an epoxy would thenbe applied between the guidewire tubular member 34 and outer tubular 44around the mandrels. Alternatively, an adhesive could be applied to theouter surface of guidewire tubular member 34 before outer tubular member44 is placed over the guidewire tubular member. The outer tubular member44 would then be positioned over guidewire tubular member 34 andmandrels inserted through the adhesive to form secondaryinflation/deflation lumens 50. The proximal end 30 of balloon 20 wouldthen be glued onto the distal end of shaft 12 with an adhesive such asan epoxy. While transition neck 40 could be formed with an adhesive, insome cases such a process may be more complicated and time consumingthan thermal compression molding. However, if the outer tubular member44 and/or guidewire tubular member 34 is formed from a non-weldablematerial such as a metal or a polyimide it may be necessary to form necktransition 40 with an adhesive. Likewise, if differences between thesoftening temperatures of the materials used to form guidewire tubularmember 34 and outer tubular member 44 are too large to permit welding,neck transition 40 may be formed with an appropriate adhesive.

FIG. 6 is a longitudinal section of catheter 10 taken through balloon 20and transition neck 40. As illustrated, secondary inflation/deflationlumens 50 provide a passage between inflation/deflation lumen 46 ofcoaxial portion 15 of shaft 12 and the interior 38 of balloon 20. FIG. 6also illustrates the melted together mass 52 of thermoplastic materialsurrounding secondary inflation/deflation lumens 50 and guidewiretubular member 34. Although the junction of the distal end of outertubular member 44 and the proximal end 30 of balloon 20 is representedby a line 54 in FIGS. 5 and 6, it will be appreciated that after thethermal compression molding process, the thermoplastic materials willhave fused together to form a continuous exterior surface through necktransition section 40.

FIG. 7 is a block diagram illustrating a method of making catheter 10.In accordance with the method, the outer tubular member and guidewiretubular member are provided as steps 100 and 102. In this variation,neck transition 40 is formed by means of thermal compression molding;hence, the tubes are formed from a thermoplastic material such as nylonor PEBA. The outer tubular member is positioned over the guidewiretubular member at step 104. A mandrel is positioned in guidewire tubularmember at step 106 to protect the guidewire tubular member fromcollapsing during the thermal compression molding process. At step 108,one or more mandrels are positioned between the outer tubular member andguidewire tubular member at the distal end of the outer tubular member.The mandrels are sufficiently long to extend through the area to becompression molded so as to form secondary lumens through the necktransition.

In this variation, at step 110 a balloon formed from a thermoplasticmaterial is then positioned over the guidewire tubular member with theproximal end of the balloon in abutting relation with the distal of theouter tubular member. In other variations of the method, the balloon maybe welded or glued to the transition neck after the guidewire tubularmember and outer tubular member have been welded together to form theneck.

Heat shrink material is then positioned around the distal end of theouter tubular member and proximal end of the balloon in the area wherethe neck transition is to be formed at step 112. In one embodiment, theheat shrink material is provided in the form of a tube that is slippedover the distal end of the outer tubular member and proximal end of theballoon. At step 114 the distal end of the outer tubular member, theinner tubular member and the proximal end of the balloon are weldedtogether by means of thermal compression molding. If the thermalcompression molding process is accomplished using a heat shrinkmaterial, the region of the transition neck may then be heated by anyconvenient means. For example, the neck transition region could beheated in an oven, ultrasonically, in a heated die, or alternatively alaser could be used to heat the neck transition region. If heated die isused in the thermal compression molding process, the die may beconfigured to compress the neck transition region, eliminating the needfor a heat shrink-wrapping.

After the thermal compression molding process is completed the heatshrink material is removed from the neck transition at step 116. Themandrels used to form the secondary lumens are then removed from theformed neck transition at step 118. The distal end of the balloon isthen attached to the guidewire tubular member. In one variation, a shimformed from a thermoplastic material may be placed over the guidewiretubular member at the location where the distal end of the balloon is tobe attached to the guidewire tubular member. In other variations, thedistal end of the balloon attached directly to the guidewire tubularmember. At step 120, a heat shrink material is placed over the distalend of the balloon and guidewire tubular member. The distal end of theballoon is then welded to the guidewire tubular member by thermalcompression molding at step 122. The heat shrink material and guidewiretubular member are then removed at steps 124 and 126.

In one variation, the guidewire tubular member is placed undercompression between the proximal and distal ends of the balloon. Thisaccomplished by using a curved mandrel or member such as a piece ofstainless steel wire to create an arc or bow in the portion of theguidewire tubular member within the balloon prior to welding the distalend of the balloon to the guidewire tubular member. After the distal endof the balloon is welded to the guidewire tubular member, the guidewiretubular member retains the arc under compression between the proximaland distal ends of the balloon. When the balloon elongates uponinflation, the arced portion of the guidewire tubular member willstraighten. This in turn reduces the forces applied to the jointsbetween the outer tubular member at the proximal end of the balloon andbetween the distal end of the balloon and the guidewire tubular memberat the distal end of the balloon when the balloon is inflated. Reducingthese forces tends to prevent delamination of the balloon from theguidewire tubular member and/or at the neck transition.

It will be appreciated by those skilled in the art having the benefit ofthis disclosure that the balloon dilation catheter shaft having endtransition described herein provides a dilation catheter having improvedinflation/deflation performance without the disadvantage inherent in theprior art. It should be understood that the drawings and detaileddescription herein are to be regarded in an illustrative rather than arestrictive manner, and are not intended to be limiting to theparticular forms and examples disclosed. On the contrary, included areany further modifications, changes, rearrangements, substitutions,alternatives, design choices, and embodiments apparent to those ofordinary skill in the art, without departing from the spirit and scopehereof, as defined by the following claims. Thus, it is intended thatthe following claims be interpreted to embrace all such furthermodifications, changes, rearrangements, substitutions, alternatives,design choices, and embodiments.

The invention claimed is:
 1. A method of making a catheter comprising:positioning an inner tubular member in the bore of an outer tubularmember, the inner tubular member extending beyond the distal end of theouter tubular member wherein the outer tubular member and inner tubularmember are brined from weldable thermoplastic materials and wherein theinner tubular member has a bore defining a guidewire lumen and whereinan annular space between the outside surface of the inner tubular memberand the inside surface of the outer tubular member define a firstinflation/deflation lumen; inserting a first mandrel into the bore ofthe inner tubular member adjacent the distal end of the outer tubularmember; inserting at least one second mandrel into the annular spacebetween the inner tubular member and the outer tubular member adjacentthe distal end of the outer tubular member; heating the outer tubularmember and inner tubular member to weld the outer tubular member to theinner tubular member at the distal end of the outer tubular member toform a transition neck, wherein the thermoplastic materials of the outertubular member and inner tubular member are bonded around the secondmandrel; removing the second mandrel from the transition neck to form asecond inflation/deflation lumen, the second inflation/deflation lumenextending from the first inflation/deflation lumen and opening at thedistal end of the transition neck; attaching a proximate end of adilation balloon to the transition neck; and attaching a distal end ofthe dilation balloon to the guidewire tubular member.
 2. The method ofclaim 1 wherein the outer tubular member is welded to the guidewiretubular member by compression thermal molding.
 3. The method of claim 1wherein the balloon is attached to the transition neck by one of weldingor gluing.
 4. The method of claim 1 wherein the balloon is placed overthe guidewire tubular member with a proximate end of the balloonadjacent the distal end of the outer tubular member prior to welding theouter tubular to the guidewire tubular member and wherein the proximateend of the balloon, the outer tubular member and guidewire tubularmember are heated to weld the proximate end of the balloon, the outertubular member and guidewire tubular member together to form thetransition neck.
 5. The method of claim 1 wherein the wherein theproximate end of the balloon, the outer tubular member and guidewiretubular member are welded by compression thermal molding.
 6. The methodof claim 1 further comprising placing a heat shrink material around thedistal end of outer tubular member and the guidewire tubular memberprior to heating the outer tubular member and guidewire tubular member.7. A method of making a catheter comprising: positioning an innertubular member in the bore of an outer tubular member, the inner tubularmember extending beyond the distal end of the outer tubular memberwherein the outer tubular member and inner tubular member are formedfrom weldable thermoplastic materials and wherein the inner tubularmember has a bore defining a guidewire lumen and wherein an annularspace between the outside surface of the inner tubular member and theinside surface of the outer tubular member define a firstinflation/deflation lumen; inserting a first mandrel into the bore ofthe inner tubular member adjacent the distal end of the outer tubularmember; inserting at least one second mandrel into the annular spacebetween the inner tubular member and the outer tubular member adjacentthe distal end of the outer tubular member; welding the outer tubularmember to the inner tubular member at the distal end of the outertubular member to form a transition neck, wherein the thermoplasticmaterials of the outer tubular member and inner tubular member arebonded around the second mandrel; and removing the second mandrel fromthe transition neck to form a second inflation/deflation lumen, thesecond inflation/deflation lumen extending from the firstinflation/deflation lumen and opening at the distal end of thetransition neck.
 8. The method of claim 7, further including the step ofattaching a proximate end of a dilation balloon to the transition neck.9. The method of claim 8, further including the step of attaching adistal end of the dilation balloon to the guidewire tubular member. 10.A method of making a catheter from an inner tubular member positioned inan outer tubular member so as to define a first inflation/deflationlumen between the inner tubular member and the outer tubular member, theinner tubular member extending beyond the distal end of the outertubular member and defining a guidewire lumen, comprising: inserting afirst mandrel into the inner tubular member adjacent the distal end ofthe outer tubular member; inserting at least one second mandrel into thefirst inflation/deflation lumen adjacent the distal end of the outertubular member; bonding the outer tubular member to the inner tubularmember at the distal end of the outer tubular member to form atransition neck around the at least one second mandrel; and removing theat least one second mandrel from the transition neck to form a secondinflation/deflation lumen extending from the first inflation/deflationlumen and opening at the distal end of the transition neck.
 11. Themethod of claim 10, further including the step of attaching a proximateend of a dilation balloon to the transition neck.
 12. The method ofclaim 11, further including the step of attaching a distal end of thedilation balloon to the guidewire tubular member.